Sexual behaviour of the green capsid bug

The green capsid bug ( Lygocoris pabulinus (L.), Heteroptera; Miridae) is an unpredictable pest in fruit orchards in North-Western Europe, since it migrates twice a year. An efficient monitoring system to predict bug damage in an orchard may reduce the use of insectices. Such a monitoring system may be developed by exploiting the sex pheromone, as L. pabulinus males are attracted by virgin females. However, attempts to identify the pheromone in the past decade have failed, which may be due to a lack of understanding of their sexual behaviour as a whole. Therefore, the sexual behaviour of the green capsid bug was studied in detail.Males and females are sexually mature 4-5 days after the final moult. EAG-responses suggest that males are more sensitive to insect-produced pheromone-type compounds, whereas females are more sensitive to plant compounds. This correlates with their behaviour, as males are attracted to virgin and mated females at long range, with and without plants. The attraction is mediated by a sex pheromone, not an aggregation pheromone, since males are not attracted to males, and females are not attracted to either sex. Sex pheromone emission is inhibited by hexyl butanoate, the alarm pheromone of L. pabulinus. Females do not show a specific calling behaviour. At close range, males are attracted to female-specific, low volatile compounds, present on female legs. These compounds are also deposited on the substrate on which females walk. At long and close range, males vibrate with their abdomen when they perceive signals from females.Matings last only 1-2 minutes, during which a compartmentalized spermatophore is formed in the spermatheca of the female. A mating plug is part of the spermatophore, inducing a refractory period in females for about 24 hours. After 24 hours, sperm is released from the spermatophore and found throughout the spermatheca and the lateral oviduct. When males have mated, they do not respond to females for at least two hours. Multiply-mated females oviposit as many eggs and live as long as once-mated females. Virgin females also oviposit eggs, but these eggs do not hatch. Under summer conditions, females oviposit preferably in potato plants.This study shows that long-range mate location by means of a sex pheromone is only part of the sexual behaviour of the green capsid bug. For pest management, the alarm pheromone of L. pabulinus may be exploited to prevent bug damage in fruit orchards.</p

More to legs than meets the eye:Presence and function of pheromone compounds on heliothine moth legs

Chemical communication is ubiquitous in nature and chemical signals convey species‐specific messages. Despite their specificity, chemical signals may not be limited to only one function. Identifying alternative functions of chemical signals is key to understanding how chemical communication systems evolve. Here, we explored alternative functions of moth sex pheromone compounds. These chemicals are generally produced in, and emitted from, dedicated sex pheromone glands, but some have recently also been found on the insects' legs. We identified and quantified the chemicals in leg extracts of the three heliothine moth species Chloridea (Heliothis) virescens, Chloridea (Heliothis) subflexa and Helicoverpa armigera, compared their chemical profiles and explored the biological function of pheromone compounds on moth legs. Identical pheromone compounds were present on the legs in both sexes of all three species, with no striking interspecies or intersex differences. Surprisingly, we also found pheromone‐related acetate esters in leg extracts of species that lack acetate esters in their female sex pheromone. When we assessed gene expression levels in the leg tissue, we found known and putative pheromone‐biosynthesis genes expressed, which suggests that moth legs may be additional sites of pheromone production. To determine possible additional roles of the pheromone compounds on legs, we explored whether these may act as oviposition‐deterring signals, which does not seem to be the case. However, when we tested whether these chemicals have antimicrobial properties, we found that two pheromone compounds (16:Ald and 16:OH) reduce bacterial growth. Such an additional function of previously identified pheromone compounds likely coincides with additional selection pressures and, thus, should be considered in scenarios on the evolution of these signals

Seasonal pattern of infestation by the carob moth Ectomyelois ceratoniae in pomegranate cultivars

Pomegranate (Punica granatum L.) orchards in the Middle East are typically composed of a mix of different cultivars in which variation in fruit infestation by carob moth Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae) has been observed. However, seasonal variation in infestation and adaptation of the carob moth to this cropping system have not been explored. We monitored the progress of fruit infestation in 10 pomegranate cultivars during the growing season of two consecutive years in pomegranate orchards of Iran. Overall, levels of infestation in fruits were strongly correlated with susceptibility to fruit cracking in pomegranate, so that cracked fruits and cracking-susceptible cultivars were infested the most. However, this pattern changed during the season. Infestation was first observed on cracking-susceptible cultivars. At this point almost all cracked fruits were infested. Towards the end of the season, infestation in uncracked fruits and cracking-resistant cultivars increased. Uncracked fruits seem better overwintering sites for carob moth as under simulated winter conditions, survival of insect larvae in uncracked fruits was >3 times higher than in cracked fruits. Taken together, our data reveal that cracked fruits of pomegranate are the better host during the growing season, while uncracked fruits better sustain carob moth population in winter. It seems therefore advisable not to grow cracking-susceptible and cracking-resistant cultivars together in the same area